Thiacyclobutane: Heat Capacity, Heats of Transition, Fusion and Vaporization, Vapor Pressure, Entropy, Heat of Formation and Thermodynamic Functions1

Abstract

Detailed studies were made of the thermodynamic properties of thiacyclobutane. The properties determined experimentally included: heat capacity of the solid and the liquid between 12 and 321/sup 0/K, transition temperature (176.7/sup 0/K), heat of transition (159.8 cal. mole/sup -1/), triple point (199.91/sup 0/K), heat of fusion (1971 cal. mole/sup -1/), vapor pressure between 48 and 132/sup 0/ (log/sub 10/ p = 701667--1321.331/(t + 224.513) (p in mm. and t in /sup 0/C)), heat of vaporization (8234 cal. mole/sup -1/ at 327.53/sup 0/K), heat capacity of the vapor (C/sup 0//sub p/ = 20.7 cal. deg./sup -1/ mole/sup -1/ at 377.20/sup 0/K.), entropy of the liquid (44.72 and 47.32 cal. deg./sup -1/ mole/sup -1/ at 298.16 and 327.53/sup 0/K., respectively), entropy of the vapor (S/sup 0/ = 68.17 and 69.75 cal. deg./sup -1/ mole/sup -1/ at 298.16 and 327.53/sup 0/K., respectively) and heat of formation (for the reaction: 3C(graphite) + 3H/sub 2/(g) + S(rhombic) = C/sub 9/H/sub 6/S(1), ..delta..H/sup 0//sub 298.16/ = 6.20 kcal. mole/sup -1/). The functions -(F/sup 0/ - H/sup 0//sub 0/)/T, (H/sup 0/- H/sup 0//sub 0/)/T, H/sup 0/ - H/sup 0//sub 0/, S/sup 0/ and C/sup 0//sub p/ were computed by the methods of statistical mechanics for selected temperaturesmore » up to 1000/sup 0/K. Values of the standard heat, standard free energy and common logarithm of the equilibrium constant of formation were obtained for the same temperatures. Spectroscopic and calorimetric data were shown to favor a planar-ring structure of C/sub 2//sub v/ symmetry for the thiacyclobutane molecule.« less